This invention generally relates to a compressor and specifically to a lubrication control system for a screw compressor.
Typically, a screw compressor includes screws that have mated helical teeth. The helical teeth engage during rotation to form a space therebetween. The space between the teeth progressively decreases between an inlet and outlet. Rotation of the screws draws low-pressure gas from an inlet into the space between the teeth and progressively compresses the gas. The compressed gas is released through an outlet opening in communication with an end of the screws.
Each of the screws is supported at the inlet and outlet ends by bearing assemblies. These bearing assemblies are supported within cavities of the compressor housing and supplied with lubricant from an oil pump through a plurality of passageways. The oil pump provides a desired lubricant pressure and flow at each bearing assembly. Orifices in flow passages to each bearing assembly are sized such that lubricant flow is governed to a desired amount at each bearing assembly. Such configurations operate acceptably for compressors where both inlet and outlet bearing assemblies require the same magnitude of lubricant flow.
However, in compressors where the inlet and outlet bearing assemblies require different magnitudes of lubricant flow, individual sizing of inlet and outlet orifices is not desirable. Utilizing different size orifices to obtain the desired lubricant flow at each inlet and outlet bearing is more difficult to manufacture and increases complexity in order to ensure that the correct orifice is installed at each location. In most cases, the inlet bearing assemblies require a lower flow rate than the outlet bearing assemblies. The resulting orifices required to reduce lubricant flow rate for the inlet bearing assemblies are relatively small as compared to orifices for the outlet bearing assemblies. Small orifices can provide the decrease in flow required, however, smaller orifices are susceptible to clogging due to debris within the lubricant. Simply, lowering the overall system lubricant flow rate is not a practical solution because such a reduction in overall lubricant flow can potentially cause control problems. Further, increasing overall lubricant flow in combination with the use of larger openings is not a desirable alternative because of the possibility of overloading the oil reclamation system.
Accordingly, it is desirable to develop a lubricant pressure control system for a compressor that provides desired lubricant flows at the inlet bearing and the outlet bearing without increasing complexity or creating potential system control problems.